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x86 idle: deprecate mwait_idle() and "idle=mwait" cmdline param

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mwait_idle() is a C1-only idle loop intended to be more efficient
than HLT on SMP hardware that supports it.

But mwait_idle() has been replaced by the more general
mwait_idle_with_hints(), which handles both C1 and deeper C-states.
ACPI uses only mwait_idle_with_hints(), and never uses mwait_idle().

Deprecate mwait_idle() and the "idle=mwait" cmdline param
to simplify the x86 idle code.

After this change, kernels configured with
(!CONFIG_ACPI=n && !CONFIG_INTEL_IDLE=n) when run on hardware
that support MWAIT will simply use HLT.  If MWAIT is desired
on those systems, cpuidle and the cpuidle drivers above
can be used.

cc: x86@kernel.org
cc: stable@kernel.org # .39.x
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Len Brown 2011-04-01 15:46:09 -04:00
parent cdaab4a0d3
commit 5d4c47e019
2 changed files with 8 additions and 0 deletions
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7
Documentation/feature-removal-schedule.txt
View file

@ -35,6 +35,13 @@ Who: Len Brown <len.brown@intel.com>
----------------------------
What: x86 "idle=mwait" cmdline param
When: 2012
Why: simplify x86 idle code
Who: Len Brown <len.brown@intel.com>
----------------------------
What: PRISM54
When: 2.6.34

1
arch/x86/kernel/process.c
View file

@ -645,6 +645,7 @@ static int __init idle_setup(char *str)
boot_option_idle_override = IDLE_POLL;
} else if (!strcmp(str, "mwait")) {
boot_option_idle_override = IDLE_FORCE_MWAIT;
WARN_ONCE(1, "\idle=mwait\" will be removed in 2012\"\n");
} else if (!strcmp(str, "halt")) {
/*
* When the boot option of idle=halt is added, halt is